Method of manufacturing multiple track, dual gap magnetic heads

ABSTRACT

Three sub-assemblies, consisting of an elongate center section having elongate, compound core members assembled with opposite sides thereof and a pair of elongate housing sections having elongate, compound core members assembled therewith, are joined with the housing assemblies sandwiching the center section assembly therebetween with an opposite end portion of each elongate core member of the center section assembly forming a magnetic circuit, including an air gap, with a corresponding end portion of an elongate core member assembled with one of the housing sections. Separation of the joined sub-assemblies substantially perpendicular to the longitudinal axes thereof at a position intermediate the opposite end portions of the elongate, compound core members results in the formation of two complete, dual gap head assemblies.

United States Patent Braun et al.

[ June 12, 1973 METHOD OF MANUFACTURING MULTIPLE TRACK, DUAL GAP MAGNETIC HEADS [75] Inventors: Richard E. Braun, James,

Lionel G. Hopkins, Lake Grove, both of NY.

[73] Assignee: Magnetic Head Corporation,

1 Hauppauge, N.Y.

22 Filed: June 9,1972

21 Appl. No.: 261,214

3,678,576 7/1972 Braun et al. 29/603 Primary Examiner-Charles W. Lanham Assistant Examine rCarl E. Hall Att0rr eyColton & Stone [57] ABSTRACT Three sub-assemblies, consisting of an elongate center section having elongate, compound core members assembled with opposite sides thereof and a pair of elongate housing sections having elongate, compound core members assembled therewith, are joined with the housing assemblies sandwiching the center section assembly therebetween with an opposite end portion of each elongate core member of the center section assembly forming a magnetic circuit, including an air gap, with a corresponding end portion of an elongate core member assembled with one of the housing sections. Separation of the joined sub-assemblies substantially perpendicular to the longitudinal axes thereof at a position intermediate the opposite end portions of the elongate, compound core members results in the formation of two complete, dual gap head assemblies,

5 'Claims, 3 Drawing Figures PAINTED- SHEET 1 OF 2 PATENIED 2W SHEEI 2 0f 2 401 V40 FIG. 3

The usual method of manufacture employed in the production of a multiple track, dual gap magnetic head involves the separate formation and assembly of each of a center section-and two housing sections with a plu-,

rality of core sections. The housing sections are subsequently joined to opposed sides of the center section in face-to-face engagement therewith, whereby respective core-sections on opposite sides of the center sections I are aligned with corresponding core sections on the housing sections to provide a plurality of magnetic circuits. Typically, the core sections assembled with the housing sections are wound with a transducing coil and are termed the active core sections while the core sections assembled with the center section simply provide a return path and are referred to as the inactive core sections. Alternatively, this arrangement may be reversed and, in many instances, both the core sections may be wound or active sections.

A substantial disadvantage inherent in the foregoing method of assembly is the necessity for the separate =formatio'n, assembly and handling of three separate components (the read and write housing sections and the center section) in the manufacture of a single, dual gap magnetic head. As is well understood by those skilled in the art, the performance standards of a dual gap head are a direct function not only of precision alignment between active and inactive core sections but, also, as between the individual magnetic circuits comprising the coacting read and write circuits associated with each of the multiple tracks. It is apparent that, in the conventional method of assembly just described, manufacturing tolerances for the completed head can be no closer than the greatestalignment tolerance that may exist between the core sections on either side of the center section and those on the two housing sections. Additionally, manufacturing costs are a direct function of the number of separate machining, assembly and handling operations required to produce the head.

A recognition of similarlimitations as applicable to the manufacture of single gap magnetic heads appears in'copending application Ser. No. 156,809, filed June 25, 1971, now US. Pat. No. 3,678,576 assigned to the assignee of the present application; wherein is disclosed a method whereby a single elongate housing may be machined in a single pass to form core receiving recesses; a plurality of compound core members are positioned in the recesses; two of the assembled housings are joined and the assembly then divided to form two single gap heads. A direct extension of this principle is not applicable to the manufacture of double gap heads since a separate center section is required and the core receiving recesses in each of the read and write housing sections are required to be of different widths. The read housing section of a typical nine track dual gap head employs active core receiving recesses having a width of 0.040 inch while the active core receiving recesseswidth of the greater active core members which would be 0.044 inch in the foregoing exemplary illustration.

This differential in active core widths between the'write and read sections is conventional to insure that each total recorded track (0.044 inch) will be read by the read section (0.040 inch) even though there may be some slight misalignment between the head and the recordable medium passing thereacross.

It is thus apparent that the opposed housing sections of a double gap head cannot be machined in a single pass since the required core receiving recess widths are different. Furthermore, even though one side of a center section might be machined along with one of the housing sections in a single pass, such an operation could not be performed on a single blank, as analogous to that of the aforesaid copending application, which would be subsequently divided because of the great disparity in thickness between the center section and a read/write housing section.

SUMMARY OF THE INVENTION The invention constitutes an improvement over the conventional method of manufacturing multiple track, double gap heads in that only three component. subassemblies are required to be worked or handled in the production of two complete magnetic heads as opposed to the required handling of three sub-assemblies in the conventional production of a single magnetic head.

This is achieved by the use of elongate, compound read/write housing and center section blanks, each of which can be machined from a single blank in a single pass to produce the core receiving recesses. After assembly of the compound sub-components with their compound core members, the same are joined to produce an elongate composite head assembly which is then divided substantially perpendicularly to the longitudinal'axis thereof to form, from the three joined coma pound sub-assemblies, two complete dual gap heads.

Although none of the individualcomponents of an individual head derived from a singly machined .blank as in the aforementioned copending application; for the reasons previously given, closer manufacturing tolerances are yet achieved because whatever machining errors may be present for a given number of operations to machine a given number of read/write or center section blanks; such errors are quantitatively halved by virtue of the requirement to machine only half as many blanks.

The use of solid copper read/write housings and solid copper center sections obviates the necessity for additional machining and/or assembly operations to provide intertrack and interhead shielding for reasons more fully set out in Applicant's copending application Ser. No. 142,563 filed May 12, 1971.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective illustrating the assembly of a plurality of compound core members with read/write housing sections and a center section prior to joining of the same to provide an elongate composite head assembly destined to become two complete dual gap heads;

FIG. 2 is a schematic illustration of the division of an elongate, composite head assembly to produce two multiple track, dual gap magnetic heads; and

FIG. 3 illustrates the two multiple track, dual gap magnetic heads produced by the division of the com- DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 are illustrated elongate, compound read and write housing sections 10, 12 and center section 14 into each of which housing sections and opposite sides of the center section have been machined nine core receiving recesses and a horizontal alignment slot in a single pass. Each of the center and housing sections are symmetrical about a central plane of division constituting a perpendicular bisector of the longitudinal axes thereof with the housing section exhibiting recesses 16 at opposite ends thereof. Core receiving recesses 18 in write housing section 12 are wider than are the corresponding core receiving recesses 20 in read housing section 10. A conventional width distinction in the case of a nine track, dual gap head is 0.044 inch and 0.040 inch, respectively. The core receiving recesses 22 on both sides of center section 14 are herein illustrated as being of equal width to the write head recesses 18 (0.044 inch). Alternatively, those center section core receiving recesses on the read head side could be 0.040 inch in width which sometimes facilitates machining operations where both one housing section and a corresponding side of the center section may be jigged together for machining in a single pass.

A plurality of elongate, compound core members 24 of appropriate width for reception in housing core receiving recesses 18, 20, each exhibit wound or active core portions 26, 28 spaced along the length thereof by an intervening vertical alignment slot 30. A like plurality of elongate, compound core members 32, corresponding in length to core members 24, comprise opposite end positions 34, 36 which will ultimately provide the inactive I cores to cooperate with each active C core 26, 28. These inactive core portions are spaced by an integral length of core member 32 which will ultimately be removed along with that length of the core members 24 comprising the vertical alignment slots 30. The compound core members 24 are assembled with the read/write housing sections, as indicated by the assembly lines relative to write housing 12 in FIG. 1, and mutually aligned therein by the positionment of a vertical alignment pin (not shown) lying across the vertical alignment slots 38 formed in each housing section and engaging the vertical alignment slots 30 in the assembled compound core members 24. Compound core members 32 are assembled with compound center section 14 as indicated by the dashed assembly lines of FIG. 1 and may be mutually aligned configuration illustrated herein; core member 24 has two active end portions in the form of conventional C cores which have been previously wound with transducing coils 42 in a conventional manner while core members 32 are depicted in that configuration to produce two inactive I cores following a division of the same as indicated in FIG. 2.

Following the assembly of nine compound core members 24 with each of the read/write housing sections and nine compound core members 32 with each side of the center section; the respective core members are aligned generally in the manner indicated by the read housing assembly and the upper side of the center section'in FIG. 1.

A plurality of male connectors are interconnected with transducer coils 42 and positioned in recesses 16 prior to the usual potting operation. The conventional male connectors have been eliminated from the drawv ing s for clarity of illustration.

Thereafter the confronting faces of the compound read/write housings and both faces of the compound center section are ground or lapped before being sandwiched together, in the manner indicated in FIG. 1, following the positionment of a desired shim material (not shown) adjacent the pole tips 44 of each active core portion 26, 28 to define the necessary air gaps between the pole tips and those endsof the associated I cores with which they will be related in the composite head assembly of FIG. 2. A horizontal alignment key is positioned between each compound housing section l0, l2, and the compound center section in respective engagement with the horizontal alignment slot 46 in each housing section and the opposed alignment slots 48 in the center section to insure that the elongate subassernblies are perfectly aligned. It will be seen that movement of the parts shown in FIG 1 into face-toface engagement results in the establishment of a magnetic circuit path, including an air gap, between each C core portion 26, 28 and an associated 1" core portion 34, 36. The compound center and housing sections may then be ioined together in any conventional manner such as by threaded fasteners (not shown) extending through aligned openings 50 in the various subassemblies to produce the composite head assembly shown in FIG. 2. The composite head assembly is then divided, such as by parallel saw cuts 40 as indicated in 7 FIG. 2, to produce the two complete multiple track, dual gap magnetic heads 52, 54 shown in FIG. 3. The heads are then polished and otherwise finished in a conventional manner.

It will be apparent that the parallel saw cuts 40 remove those intermediate portions of compound core members 24 comprising the vertical alignment slots 30 as well as the corresponding intermediate portions of compound core member 32 resulting in the formation of the individual magnetic circuits in the finished head which include the air gap 56.

Each of the finished heads include identical read and write housing sections 58, 60 and identical center, sections 62.

We claim 1. A method of manufacturing multiple track, dual gap magnetic heads, comprising; providing first and second pluralities of elongate, magnetic core members, each having core portions spaced along the longitudinal axes thereof; providing a winding on each of said spaced core portions; providing third and fourth pluralities of elongate, magnetic core members, each, having core portions spaced along the longitudinal axes thereof; assembling a like number of said first and second plurality of core members with first and second elongate. housings, respectively; assembling a like number of said third and fourth-plurality of core members I with opposite sides, respectively, of an elongate center section; joining the housing assemblies in face-to-face engagement with said opposite sides of said center section with each of the spaced core portions of each housing assembly defining individual magnetic circuits, including transducing gaps, with spaced core portions of the center section assembly; and dividing the joined housing and center section assemblies at a position intermediate the spaced core portions of the assembled core members to produce two dual gap magnetic heads.

v 2. A method of manufacturing multiple track, dual gap magnetic heads, comprising; providing first and joining the housing assemblies in face-toface engagement with said opposite sides of said center section whereby each of the spaced core portions of each housing assembly defines an individual magnetic circuit, including a transducing gap, with a spaced core portion of the center section assembly; and dividing the joined housing and center section assemblies at a position intermediate the spaced core portions of the*assembled coremembers to produce two dual gap magnetic heads.

3. The method of claim 2 including the prior step of machining core member receiving recesses in opposite sides of said elongate center section and in each of said elongate housings.

4. The method of claim 3 including the step of machining greater width core member receiving recesses in one of said housing than in the other.

5. The method of claim 4 wherein the core member receiving recesses in each said elongate housing is machined in a single pass. 

1. A method of manufacturing multiple track, dual gap magnetic heads, comprising; providing first and second pluralities of elongate, magnetic core members, each having core portions spaced along the longitudinal axes thereof; providing a winding on each of said spaced core portions; providing third and fourth pluralities of elongate, magnetic core members, each, having core portions spaced along the longitudinal axes thereof; assembling a like number of said first and second plurality of core members with first and second elongate housings, respectively; assembling a like number of said third and fourth plurality of core members with opposite sides, respectively, of an elongate center section; joining the housing assemblies in face-to-face engagement with said opposite sides of said center section with each of the spaced core portions of each housing assembly defining individual magnetic circuits, including transducing gaps, with spaced core portions of the center section assembly; and dividing the joined housing and center section assemblies at a position intermediate the spaced core portions of the assembled core members to produce two dual gap magnetic heads.
 2. A method of manufacturing multiple track, dual gap magnetic heads, comprising; providing first and second pluralities of elongate, magnetic core members, each having core portions spaced along the longitudinal axes thereof; providing third and fourth pluralities of elongate, magnetic core members, each, having core portions spaced along the longitudinal axes thereof; assembling a like number of said first and second pluralities of core members with first and second elongate housings, respectively; assembling a like number of said third and fourth pluralities of core members with oPposite sides, respectively, of an elongate center section; joining the housing assemblies in face-to-face engagement with said opposite sides of said center section whereby each of the spaced core portions of each housing assembly defines an individual magnetic circuit, including a transducing gap, with a spaced core portion of the center section assembly; and dividing the joined housing and center section assemblies at a position intermediate the spaced core portions of the assembled core members to produce two dual gap magnetic heads.
 3. The method of claim 2 including the prior step of machining core member receiving recesses in opposite sides of said elongate center section and in each of said elongate housings.
 4. The method of claim 3 including the step of machining greater width core member receiving recesses in one of said housing than in the other.
 5. The method of claim 4 wherein the core member receiving recesses in each said elongate housing is machined in a single pass. 